Re: C/N for digital reception

At 12:18 25.04.1997 +0500, you wrote:
>Hello Dr.Dish.
>Thank you for your information.
>Let me ask one question.
>All of us know what Career/Noise level is suitable for
>analogue reception. But what level of Career/Noise is
>suitable for digital reception ?
>With best regards.
>Serghey Kolosha
For analogue reception C/N influences the final S/N ratio. For digital
transmission it is the BER (Bit Error Rate) which counts. The picture/sound
performance depends on the Eb/No value corresponding with a certain BER.
Eb/No means: Energy per Information Bit/Noise Power. In order to get the
ITU-quality level 5 a BER of 10 (up -6) is nessesary. For analogue downlink
a S/N of 40dB delivers a good quality. 15dB S/N in a digital downlink gives
the same result. To determine the Eb/No: C/N+10 log (1/data rate in bit/s)+
10 log (tx-bandwidth in Hz). If you compare a digital downlink budget with a
analogue, you see that a lower C/N is required for digital transmissions
(for instance: 11.5dB(analogue)= around 9.9dB (digital).
Christian Mass (Dr.Dish)
Editor of TELE-satellite magazine (http://www.TELE-satellit.com)
Producer of drdish@tv, Europe´s first satellite info-channel

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